1. Field of the Invention
The present invention is directed to a solid polymer electrolyte fuel cell.
2. Discussion of the Background
A variety of fuel cells are effective to cope with global environmental and resource problems such as CO2 discharge regulation for the prevention of atmospheric pollution and the shortage of oil resources. However, the solid polymer electrolyte fuel cell has been spotlighted due to the clean-fashion operation, high density in energy and charging-free characteristics. Thus, in many countries such as Japan, research and development of the solid polymer electrolyte fuel cell is making rapid progress.
As illustrated in FIG. 8, in a conventional or prior art solid polymer electrolyte fuel cell two gas-permeable, porous, electrically conducting gas diffusion layers, are provided at both sides of a polymer electrolyte membrane 900. A catalyst layer 950 is interposed between one side of the polymer electrolyte membrane 900 and the gas diffusion layer 910. A catalyst layer 960 is interposed between the other side of the polymer electrolyte membrane 900 and the gas diffusion layer 920. An external circuit 930 as an external load is interconnected between the gas diffusion layers 910 and 920. The gas-permeable, porous, electrically conducting gas diffusion layer 910 and the catalyst layer 950 constitute a fuel electrode, while the gas-permeable, porous, electrically conducting gas diffusion layer 920 and the catalyst layer 960 constitute an oxidant electrode.
In the solid polymer electrolyte fuel cell having the above structure, a fuel gas which is in the form of a hydrogen gas or a hydrogen-containing gas flows through the gas diffusion layer 910 and reaches the catalyst layer 950. Then, the following electrochemical reaction occurs:
2H2xe2x86x924H++4exe2x88x92
resultant proton H+moves toward the oxidant electrode by passing through the polymer electrolyte membrane 900. At the oxidant electrode oxygen or air are used as oxidants. Simultaneously, the electron exe2x88x92 generated at the fuel electrode moves, by way of the external circuit 930, toward the oxidant electrode. The electrical resistance which results from the series connection of the catalyst layer 950 and the gas diffusion layer 910 drops the voltage, thereby lowering the cell output.
At the side of the oxidant electrode the oxidizing gas containing oxygen and the electron exe2x88x92 which comes from the external electric circuit move through the gas diffusion layer 920 and reach the catalyst layer 960, at which the following electrochemical reaction or reduction occurs:
O2+4H++4exe2x88x92xe2x86x922H2O
Some of the formed water enters the polymer electrolyte membrane 900 and diffuses toward the fuel electrode due to a concentration gradient. The remaining water is evaporated, diffuses into a gas passage (not shown) by way of the catalyst layer 960 and the gas diffusion layer 920. It is then discharged outside together with an off gas of the oxidant gas. The diffusion path of the water depends on the length of the catalyst layer 960 and the gas diffusion layer 920. As the diffusion path of the water becomes longer the produced water becomes difficult to be discharged, in addition to the increase of the electrical resistance and the increase of the reaction gas diffusion resistance. This causes an easy condensation of water, with the result that the supply of reaction gas is disturbed. Thus, the catalyst utilization is lowered, thereby lowering the cell characteristics.
In view of the foregoing circumstances, there is a need for a solid polymer electrolyte fuel cell which is free from the above drawbacks.
It is an object of the present invention to provide a solid polymer electrolyte fuel cell which overcomes the above drawbacks.
These and other objects are achieved according to the invention, the first embodiment of which includes a solid polymer electrolyte fuel cell, comprising:
a first gas diffusion layer;
a second gas diffusion layer; and
a catalyst layer;
wherein said first diffusion layer, said second gas diffusion layer and said catalyst layer are arranged on each side of an electrolyte;
wherein said electrolyte is an ion exchange membrane;
wherein said electrolyte is sandwiched;
wherein said catalyst is dispersed in a cellular dispersion layer which constitutes the gas diffusion layer.
Another embodiment according to the present invention includes a solid polymer electrolyte fuel cell comprising:
an electrolyte;
a gas diffusion layer arranged on each side of the electrolyte; and
an electrode catalyst dispersed in a gas diffusion layer,
wherein said electrolyte is an ion exchange membrane.
Yet another embodiment according to the present invention includes a gas diffusion layer comprising:
a base flat member having at least one pore;
a catalyst; and
at least one catalyst supported particle,
wherein said catalyst supported particle is dispersed in said pore of said base flat member.